An evaluation of scale-dependent effects of atmosphere-glacier interactions on heat supply to glaciers

Scale-dependent atmosphere-glacier interactions operate over a glacier surface as the surface has different thermal and radiative characteristics from those of the surrounding ground. In order to evaluate heat supply to the glacier surface in the main ablation period, three main interaction processes are considered: advection, glacier wind, and multiple reflection of solar radiation. The amount of heat supply was calculated for the equilibrium line altitude (ELA) by assuming a simple rectangular-shaped glacier, and by applying meteorological and glaciological data for four different glaciated regions (Tien Shan, Patagonia, west Kunlun and Nepal Himalaya). The total heat supply due to the above three processes had the common tendency of being smallest for glaciers of 1 to several kilometres in length, and largest at 16 km, which was the maximum length considered in this study. Among the cases, the Tien Shan showed a daytime heat supply higher by 2.3 MJ m−2for a 16km-long glacier compared with a small glacier 2 km in length. Relating this difference directly to ELA, an ELA approximately 300 m higher might be expected for a long glacier than a short one, assuming the same amount of solid precipitation. Glacier inventory data for China support this tendency, but the calculated value is slightly larger than that observed. The results show that there is a possibility that responses in glacier variation to climate change may be modified considerably through scale-dependent atmosphere-glacier interactions.